Help me get this bike up to its potential

[Braaapitron]

I bought a 4mil j arm bamshee stroker has fmf pipes stage4 trinity head with 20cc 9mm domes charity intake and uni pod filters and bigger carbs not 100% on the mm has stock cylinders and no porting it had stock pistons in it and hasnt ran properly yet bottom of one of the stock pistons snapped off so I ordered new wiseco pistons still waiting on one more to show up but the bike has been a slug oh and it has a spacer plate I just ordered a timing plate and reeds and carb sync tool amd jets with the new pistons my questions are 

1. Was it running horrible cuz the pistons were wrong? 

2 what should my timing be set to when installing the plate 

3. I'm 1100 above sea  level where should I start with jetting 

4. Do I need to get it ported or different cylinders 

5. Is this set up a 421 cc ?

Thanks guys for any info this is my second banshee but last one i had went 2 seasons without having to even change a plug before I sold it and regretted it for a year before finally saving up for this one I trusted the guy and paid 5g all to be very disappointed in his work now I have had it a couple months and finally got motivation to get the beast unleashed  so pretty new to working on them I'm pretty mechanically inclined but not a small engine mechanic in any means

[375hp banshees]

Verify its a 4mil. Crank
Verify piston #'s
If pistons were wrong, the cheep way is buy correct pistons & try & get it running & Reassess.
Better solution ~send to reputable builder get correct porting, check crank & ditch the spacer.

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